Joint for electric cables



Oct. 30, 1934. E, D. EBY

JOINT FOR ELECTRIC CABLES Filed Jan. 19, 193g Patented oct. 3o, 1934 UNITED STATES JODIT FOR ELECTRIC CABLES Eugene D. Eby, Pittsfield, Mass.,a.ssignor to General Electric Company, a corporation of New York Application January 19, 1932, Serial No. 587,474

15C1aims.

The present invention relates to cables for transmittingelectric currents for power purposes at high potentials. Such cables comprise a hollow conductor surrounded by a body of insulation and an enclosing metal sheath. Lo- I cated within the channel of the hollow conductor is a body of insulating fluid, of which thin oil is an illustration. Because the fluid expands and contracts with changes of temperature, the established practice is to provide variable capacity reservoirs at spaced intervals along the length of the cable and connect them to the channel within the conductor. Because of electrical considerations occasioned by the high potential, it has been the practice to make the connections between the reservoirs and the channel only through the medium of fluid stop joints. Such joints as their name implies are used to electrically connect one cable section or length with another and at the same time prevent the uid in one section or length from entering the connected section on the other side of the joint. These joints by reason of their necessarily complex structure are expensive and are required wherever it is necessary to limit the hydrostatic pressure on a given part of the cable due to the irregular prole of the ground over which the cable is laid. On the other hand, there are many places where a stop joint as such isunnecessary but where it is necessary to connect a reservoir to the cable. The ordinary or so called normal joints used to connect cable lengths and permit uid to ow between them while substantially cheaper than stop joints do not permit of connecting a cable channel to a reservoir. In this connection I may say that the very `high voltages transmitted by such cables is the primary reason why normal joints as heretofore made arel unsuited for the 4o purpose.'

My invention has for its object the provision of an improved simple form of joint which is less expensive and simpler than the stop joints and only slightly more expensive than the normal joints for feeding fluid to the cable with the ultimate result that the total cost of a cable system may be appreciably reduced. To state the matter in another way, with my improved construction stop joints need only be employed where necessary to break up the static head of the huid instead of using them at every place along the cable length whereit is required that a reservoir shall be connected.

For a consideration of what I believe to be to the accompanying description and the claims appended thereto.

In the drawing Fig. 1 illustrates in longitudinal section a joint embodying my invention; Fig. 2 is a cross-section through the connectoi` at the center of the joint; Fig. 3 illustrates my invention as applied to a uid stop joint whereby its construction may be simplified; Fig. 4:

is a cross-section through the connector at the center of the joint, and Fig. 5 is a detail view of a Ierrule for a feeding tube.

In the drawing 5 indicates the lead or equivalent sheaths of two cable lengths which are to be connected electrically. 6 indicates the hollow stranded conductors, the hollow space in the center forming a channel for the fluid insulation, and, 7 the layers of factory applied insulation, such as paper. The insulation is decreasm in thickness toward the connector by a series of steps 8. 9 and 10 indicate members of a two part metal connector, each having a central bore 1l through which insulating fluid such as oil is free to flow from the channel of one length of cable to the other. Each half connector is provided with a two-way plug valve 12 which is used for flushing purposes in installing the cable iii the underground ducts. In the position shown they are open to permit uid to ow from one cable channel to the other. When the valves are turned through an angle of degrees the ow is shut oi. Each half connector has a socket in which the ends of the stranded conductors are located and soldered. In the outer wall of the socket is a small hole through which solder may be introduced for making positive contact between cable conductor and connector. Inside of each conductor and forming a continuation of the hollow core or channel thereof is a short tube 13 which supports the conductor strands at the connector.

Completely enclosing the connector and the adjacent ends of the insulated conductors is a bocw of insulation 14 of any suitable material of the proper shape, diameter and length. As an illustration, but not as a limitation, the body maybe composed of varnishecl cambric tape having high insulating, low loss properties and applied layer by layer until the desired amount has been thus applied. In taping, that portion between the ends ofUv the connector and the various steps in the factory applied insulation, is rst applied as indicated by the numeral 15. As a result of this the cable presents a smooth cylindrical surface from one end to the Qilfl` 'After this is done the outer part 16 'Ill example be made of copper tape or perforated metal ribbon. Enclosing the parts of the joint v is a two-part metallic sleeve or casing 18, the

ends of which are soldered to the sheaths by 'wiped soldered joints 19. The parts of the casing` are similarly united bya joint 20. The

casing and ground shield 17 are connected at' or near the center by a contact member 21.

Considering now the means for getting fluid into and out of the channel of the cable, the highest electrical stress on the joint insulation or dielectric material is in the region of the connector and decreases toward the periphery of the insulating body, hence it is particularly important that there shall be no voids or space in said region. It is also of the greatest importance that there be no opportunity for leakage current to pass from the connector axially along the insulation to the cable sheath between the factory insulation and the tape wrapping and also between the layers of said wrapping. It is to be borne in mind that suitably impregnated 'insulation is a substantially better insulation than oil hence it becomes important to make the oil or fluid carrying conduit leading to'the outside comparatively long and of small cross-section. These important and vnecessary results are obtained by the following means: The left-hand connector part is provided with an opening 25 or' a series of openings in its upper side which communicates with a port 26 in the plug valve 12. Extending into the openings r-recesses are smallconduits or unitary tubes 2'7 of which four are shown, but the number may be greater or less. In order to avoid sharp bends in the tubes the recesses 25 are slanted in the direction the tubes finally occupy. The tubes are anchored in the recesses by a lling of suitable cement 28. The tubes should be made of high grade insulation, be reasonably flexible and not adversely aiected by the oil in the cable. For this purpose the conduits or tubes may be made of an alkyd resin or equivashall not be unduly stressed electricallythey are purposely made long and of small diameter bore. They are coiled or wound around thecable and to obtain the necessary length, and are also provided with` a certain amount of slack to permit the left-hand casing part to be slipped back over the cable while the jointing operation is carried out. For the purpose of illustrating my invention, it is shown in connection with a 69 kv cable, but its use is `not limited thereto. As further illustrating my invention, the unitary conduits or tubes may have -an inside diameter of one-eighth of an inch and alength of six ,feet whichlatter is many times thelength of one-half of the joint. part is embedded in the body of wrapped insulationA or reinforcement and the remainder 'forms the slack which is loosely wrapped around the electrostatic shield which covers the reinforcement or insulating body. The shield is cut away sufficiently to permit the tubes to pass through itwithout injury thereto.

of um total length :lA

subsequent to which As previously stated Vthe insulation is most highly stressed near the conductor. To reduce the stress on the oil within'the unitary tubes as `rapidly as possible the turns of the tubes or conduits instead of being: of the same diameter and occupying the' same cylindrical surface, are so arranged that each successive turn or wrap is of larger diameter than thepreceding one until the periphery of the body or joint insulation is` reached. In order toreduce the danger of faulty insulation, the turns also progress or have a pitch like a screw thread from the inner end to the outer surface of the insulating body as distinguished from being coiled one around the other in the same perpendicular plane. By thus arranging the tubes in an open helix or spiral of ever increasing diameter, it becomes a relatively simple matter to so wind the tape comprising the insulating body that no spaces or voids are formed around each turn of the tubes except those occasioned by the fact that the. surfaces presented by the tubes are round; These spaces which are very small maybe lled as the wind- Y tion is lremoved therefrom withtape insulating between, and that the other turns increasingv Ain diameter as. they do rapidly move out ofthe zone of highest stressv to that outside of the electrostatic or ground shield 17.

To facilitate the work of connecting the tubes to the connector 9 and to a header or fitting teaming the receiving holes both' in the connector and header. The tubes are secured in the ferrules by means of Glvptal varnish* or its equivalent. v

In order te establish communication vwith the tubes from the outside, a header is provided and Supported by that half of the joint casing which immediately surrounds the tubes.

It comprises `a member 31 that is soldered to the casing and is provided with a central plug 32 and an external screw thread to receive' the cap 33. 'I'he plug has as many openings as there are tubes and in these openings are secured the metal ferrules 30 on the'tube ends. The plug is held in position by a perforated plate 34 which rests on the upper edge of the member 31', the plate and plugl being connected by a' small screw. The cap has an opening to receive the pipe 35 leading'to a reservoir of any suitable construction, for example, that shown in my patent No.1,823,73l, dated September 15, 1931. The pipe is secured in place by a suitable screw threaded nut 36 and tapered cone which fo'm a fluid-tight connection. l I

At installation the parts of the connector are soldered tothe cable ends and then flushed to free them of foreign matter 'in the usual way, operation the insulation is applied.

Brief reference has been made to applying the reinforcement or insulating body andthe tubes. After the taping 15 has been wound over the stepped part of thefactory applied insulation and the connector, the ferrules on the inner ends of the tubes are forced into the connector and properly sealed. Tape insulation or reinforcement is then applied to form a covering of substantially conical form, increasing in diameter from right to left from the connector to form 4seats for the turns of the tubes, as indicated in 1. Over these seats are wrapped the tubes after which the remainder of the reinforcement or insulating body is applied and later the ground shield. As a result of the winding operation, the tubes and layers of insulation are interspaced. During the wrapping operation the outer ends of the tubes are temporarily wrapped around the cable, and they may or may not be provided with ferrules at the time. After the outer ends of the tubes are secured in the plug 32, the latter is seated in place and retained by the perforated plate 34 and screw. After the tubes have been ushed of foreign matter. their to facilitate the taping` operation. After the joint is fully insulated and shielded, the parts of the casing are moved to the position shown and soldered to each other and to the cable sheaths. Later the pipe 35 is connected and also the reservoir.

After the connector members are sweated or soldered to the cable ends and to each otherl and the ferrules on the inner ends of the tubes secured to a connector part, the plug valves 12 are opened and the reservoir on the opposite end of the cable length is caused to slowly feed fluid into the cable, the eil'ect oi which is to insure a slow iiow of iluid through the tubes and prevent the admission of air or other foreign matters to the tubes and cable channel. Although the right-hand plug valve is not associated with a set of feeding tubes, it is provided with a port 39 for iiushing purposes. Before the casing is nally sealed it is preferable to evacuate it and then ll it with degasiiied oil. For this purposethescrewthreadedplugilmaybeused, the practice in this respect being that normally employed.

It is desirabie to connect the inner ends of the tubes to the connector and the outer ends to the header rather than to terminate the tubes atthesurfaceofthebodyofinsulationasthis affords a better control of the movements of the iluid between reservoir and cable. 'Ihe arrangement is also desirable in the event of a cable failure as there will be less tendency to loss of fluid and deterioration of the insulation. However, in the broader aspects of my invention, the tubes may terminate in other ways. Also the tubesinsteadof beingroundmaybeotherwise shaped, provided they are of such a character asnottobecrushedwhenthetaperedbodyof insulation is applied.

My invention thus far has been described as a modified form o. normal join "but it is also applicable. to and substantially simplifies the construction and cost of joints of the semi-stop vtypeasillustratedinligs.3and4. Inthese lfiguresthecorinectorparts40and4linsteadof veyed to the outside of the casing by means of headers as previously described. In some cases it may be `desirable to connect only one member` ofaconnectortoasetoffeedingtubesandto rely upon another joint at some other part of the cable length or section to take care of the demands of the cable as the fluid alternately heats and cools.

with joints having electrostatic shields but it is also useful in connection with non-shielded joints when the necessity of feeding oil to the cable exists. 4

whatlclaimasnewanddesiretosecureby Letters Patent oi theUnitcd States is:

l. A joint for iluid lled cables hollow insulated conductors, a connector for uniting adjacent ends of the conductors having a fluid. containing therein, iiuid insulation filling the conductors and connector, a body of insulation enclosing the connector and adjacent insulated ends of the conductors and comprising tape arranged in concentric layers, an enclosing casing for the joint which is sealed at its ends to the cables, and a. duid conveying -conduit made ofa unitary piece oi tubing ar` ranged in spiral i'orm, the individual turns of which are embedded be the successive layers of the body-oi insulation, the inner end of the tubing opening into a channel within the connector and the cute-rend terminating in a wall of the casing.

2. A joint for fluid lled cables comprising hollow insulated conductors, a tor for uniting adjacent ends of the conductors having a fluid containing channel therein, fluid insulation filling the conductora and connector, a body of insulation enc the connector and adjacent insulated ends'oi the conductors and comprising concentric layers of tape, an enclosing for the joint which is sealed atits ends to the cables. and a uid carrying unitary conduit made oi non-conducting ma sprally wrapped about an end of a conductor within the body of insulation, the turns of the spiral being in between layers of tape and displaced laterally one from another and increasing in diameter outwardly from the axis oi the conductor, the inner end oi the conduit opening into the channel in the connector and terminating at the other end at a point outside of said body.

3. A joint for fluid iilled cables comprising hollow insulated conductors, a connector for uniting adjacent ends of the conductors having a fluid containing channel therein, duid insula- My invention has been described in connection Y tion illling the conductors and connector,l a body of insulation enclosing the connector and adjacent insulated ends of the conductorsand comprising concentric layers of tape, an enclosing casingforthejointwhichissealedatitsendsto the cables, and a tube made of non material spirally wrapped about an end of a conductor with the turns thereof located between layers of tape at progressively diierent distances from the axis thereof, one end of the tube entering the connector and its other end terminating outside of the body where the electrical stress on the body is low.

4. A joint for uid nlled cables comprising hollow insulated conductors, a connector for uniting adjacent ends of the conductors having a fluid containing channel therein, uid insulation llv ing the conductors and connector, a body of insulation enclosing the connector and adjacentV insulated ends of the conductors and comprising concentric layers of tape, an enclosing cas-- ing for the joint which is sealed at its ends to the cables, and a ilexible insulating unitary tube of i small diameter and of a length greater than that of one half of the joint, the tube being embedded between layers of vtape forming the body and extending through it from the connector where the electrical stress'is at a maximum to a point in its outer surface where the stress is at a minimum, said tube conveying fluid to and from the channel in the cable.

`5. A joint for uid lled cables comprising insulated conductors each having a channel containing fluid insulation, a connector uniting adjacent cable ends, a body of insulation covering vthe connector and parts of the conductor insulations, said body comprising tape=wrappings arranged in layers, an enclosing fluid tight casing for the joint, and parallel unitary tubes of insulating material of small diameter and relatively great length compared to the axial length of the j conductors comprising concentric'layers of material, a casing for the joint, a exible unitary tube of insulating material .wound around thev body and embedded therein, the inner end of the tube being located in the recess in the vconnector and the outer end extending through the periphery of the body and terminating at the casing wall, and a means carriedby the casing in which the outer end of the tubeis seated. o A

'1. A joint for uid filled cables comprising insulated conductors, eachv having Aa uid con-1 taining channel, a connector electrically uniting adjacent conductor ends a fluid receiving bore communicating with a channel, a body of insulation enclosingthe' connector and adjacent ends of the conductors, a fluid tight casing for the joint, small parallel unitary tubes of insulation embedded within rthe body and wound to form an open spiral, the diameters of the turns of the spiral increasing from the connector outwardly to remove the'outer ends from the region of highest electrical stress, the inner ends of the tubes communicating through the connector with a cable channel, and means carried by a wall of the casing to receive the outerends of the tubes.

8. A joint for fluid filled cables comprising insulated conductors, each having a uid containing channel, a connectorl electrically uniting great length spirally wrapped about a conductor to convey uid between the channel and the outside of the casing, one part of the tube being embedded within the body between layers thereof and the remainder loosely overlying the body to permit a part of the casing to be moved over the joint after the body and tube are assembled in place.

. 9. A joint for uid fiilled cables comprising insulated conductors, each having a fluid containing channel, a connectorfor electrically connecting adjacent conductor ends also containing uid, a uid tight casing for the joint, a body of insulation foruthe connector and cable ends, and small exible tubes of insulating material forl conveying uid from a conductor channel to the outside of the casing, said insulation and tubes being wrapped around an end of a conductor in layers, the tubes forming a spiral of gradually enlarging diameter with the turns thereof interspaced with layers of said body and extending from a cable channel to the periphery of the body.

10. A joint for uid filled cables comprising insulated conductors, each having a iiuid lled channel, a connector electrically uniting adjacent conductor ends and having a bore to permit paage of fluid, a two part casing for and in spaced relation to the joint, the plane of division being perpendicular to the axis-of the joint, a header carried by 'a wall of one part of the casing, a body of insulation enclosing the connector and adjacent conductor ends, and exible insulating unitary tubes Aarranged in parallel in the form of an open spiral and embedded at spaced intervals in the body for a portion of their length, the remainder being movable` in the space between the body and the inner wall of the casing to permit movements of a part of the casing with respect to the joint, the inner ends of the tubes communicating with a conductor channel and their outer ends terminating in the header.

11. A cable joint' comprising insulated conductors, each containing a channel lledowith uid.

insulation, a connector electrically uniting ad- I jacent conductor'ends and preventing the iiow of iluid from one channel to another, a body of insulation enclosing the connector and adjacent insulated ends of the conductors and comprising concentric layers of material, a uid tight casing for the joint, and a spirally arranged unitary .tube of insulating material embedded in rSaid body between layers thereof and connected at its inner end to one of the channels and communicating at its outer end with the outside of the casing.

12. A cable joint comprising insulated conduc tors, each containing a channel lled with uid insulation, a connector electrically uniting adjacent conductor ends and preventing the ow casing for the joint, and two sets of spirally arranged unitary tubes of insulating material both -embedded in said body between layers thereof and connected at their inner ends to different cable channels and communicating at their outer ends to dierent regions outside of the casing.

i3. A cable joint comprising insulated conductors, each containing a channel lled with fluid insulation, a connector for electrically uniting adjacent conductor ends, a body of insulation enclosing lthe connector and adjacent insulated ends of the conductors, a fluid tight casing for the joint, a spirally arranged tube of insulation embedded in the body, and metal ferrules on the ends of tube, one of said ferrules being seated in the connector in communication with a conductor channel, and the other of said ferrules being seated in the joint casing and opening to the outside thereof.

le. A joint for fluid lled cables comprising insulated conductors, each having a channel l'led with insulating uid and a metal sheath, a hollov/ connector for electrically uniting the cable ends, two-way shut-off valves denitely positioned in the connector, a body of insulation enclosing the connector and adjacent insulated ends of the conductors, an enclosing metai casing sealed to the sheaths, a ground shield overlying the said body and connected at its ends to the sheaths, a spirally arranged conduit within said body having its inner end secured in the connector at the side of the valve permitting control of uid from the channel to the conduit, and its outer end extending through the ground shield, and a header carried by the casing in which the outer end of the conduit is seated.

15. A cable joint comprising insulated conductors, each containing a central channel filled with uid insulation, a two-part connector for uniting the conductors and containing a channel for establishing communication between those in the conductors, insulation enclosing the connector and conductor ends, an enclosing casing, a conduit of insulating material forming a spiral and located principally within the insulation and communicating at one end with the channel in the connector and the other end terminating outside of the insulation, and a valve located in the connector for controlling the passage of fluid through it from one conductor channel to the other and also the passage of fluid through the said conduit.

EUGENE D. EBY. 

